react how to refs

reactRefs.jsx

import React from 'react';
import './App.css';
import './index.css'

function App() {
  return (
    <div className="App">
      <Parent/>
    </div>
  );
}

class Parent extends React.PureComponent {
  constructor(props) {
    super(props);
    this.state = {};

    this.handleButtonRef = React.createRef();
  }

  handleDickKnowWhat = () => {
    this.handleButtonRef.current.handleClick()
  };

  render() {

    return (
      <>
        <h1>Parent</h1>
        <div className="myblock">
          <Child1 ref={this.handleButtonRef}/>
          <Child2 handler={this.handleDickKnowWhat}/>
        </div>
      </>
    )
  }
}

class Child1 extends React.PureComponent {
  constructor(props) {
    super(props);
    this.state = {
      title: 'some',
      isActive: false,
    }
  }

  handleClick = (e) => this.setState(({ isActive }) => ({ isActive: !isActive }));

  render() {
    return (
      <div style={{border: '1px solid purple'}}>
        <h2>First Child</h2>
        {this.state.isActive && (<h3>{this.state.title}</h3>)}
        <button onClick={this.handleClick}>
          child button
        </button>
      </div>
    )
  }
}

class Child2 extends React.PureComponent {

  render() {
    const { handler } = this.props;
    return (
      <div style={{border: '1px solid violet'}}>
      <h2>Second Child</h2>
        <button onClick={handler}>toggle child 1</button>
      </div>
    )
  }

}

export default App;